Three-dimensional modelling of ship-induced flow and erosion

Abstract

Ship-induced erosion by propeller jets causes considerable damage in canals, harbours, locks and waterways. Jet velocity reaching the bed could be as high as 15 m/s depending on the ship and the machinery. The objectives of the present study were to investigate the nature of the propeller jet flow and to estimate the rate of erosion caused by the jet. Three-dimensional numerical models can be used to simulate ship-induced propeller flows provided the propeller can be replaced with a simpler geometry. The study modelled the propeller flow by one lower and one upper jet flow. The turbulent characteristics, such as the turbulence intensities and the energy balance of the lower jet, are similar to a flat wall boundary layer flow. The application of the three-dimensional flow model was extended by numerically solving the sediment continuity equation. The computations were based on the lower part of the jet velocity profiles. The method enables the scour cavity induced by a stationary ship with a running engine to be calculated. The computed scour cavity agreed well with the field data.